yes!! I join group study that study R-programming... so I really tried..only to fail and made many erros.. I really don't know how to perform this... -- View this message in context: http://r.789695.n4.nabble.com/hi-l-have-a-question-please-help-me-tp2307569p2308091.html Sent from the R help mailing list archive at Nabble.com.